Postgresql Two-phase Commit Transaction Identifier

Is it possible to perform a two-phase commit in Postgresql when the databases exist on the same server?

As a simple test, I would connect to the first database and run:

BEGIN;
PREPARE TRANSACTION 'test';

and in a new terminal tab I would connect to the second database and run the same commands. This outputs the error:


ERROR: transaction identifier "test" is already in use

So my solution was to simply not use the same transaction identifier across all databases. The Transaction Manager can keep track of the various identifiers and commit the databases accordingly.

Seems ridiculously obvious so please correct me if I'm wrong.

StackExchange Database Administrators Q#34799, answer score: 3